1+4+7+10+13+16+19+22+25+28+31+34+37+40+43+46+49
=(1+49)+(4+46)+(7+43)+(10+40)+(13+37)+(16+34)+(19+31)+(22+28)+25
=50+50+50+50+50+50+50+50+25
=50×8+25
=400+25
=425
祝你开心
(1+49)+(4+46)+(7+43)+(10+40)+(13+37)+(16+34)+(19+31)+(22+28)+25=50X8+25=425
(1+49)*8+25
425